(2) Mystery Tube

• Student Version- Develop and refine a model for a system that can explain your  observations.

• Instructor Version

NGSS Engineering Standards

• NGSS Engineering Standards

"Black Box" Investigations

A "black-box" investigation in science refers to an inquiry where the internal workings of a system or process are not known or directly observed. Instead, researchers focus on understanding the system by analyzing its inputs and outputs. The term "black box" suggests that the internal mechanisms are hidden or not accessible, but by studying how the system responds to different inputs, scientists can infer how it operates.

This type of investigation is commonly used in situations where the system is too complex to fully understand, where direct observation is impossible, or where the focus is on the functional behavior rather than the specific details of the system's internal structure. The goal is to create a model or explanation of how the system works based on its external behaviors.

Rutherford's Gold Foil Experiment (1911): - Dense nuclei of atoms

• Overview: Ernest Rutherford conducted an experiment where he directed alpha particles at a thin sheet of gold foil. Most particles passed through the foil, but some were deflected at large angles.

• Inference: Rutherford concluded that atoms have a small, dense, positively charged nucleus, as opposed to being a uniform "plum pudding" of positive charge. The nucleus was inferred by observing the deflection of particles, without directly observing the nucleus itself.

Young's Double-Slit Experiment (1801): - Wave nature of light

• Overview: Thomas Young shone light through two closely spaced slits and observed the resulting pattern on a screen. The pattern displayed interference fringes, which were unexpected if light were purely a particle.

• Inference: This experiment led to the inference that light behaves as a wave, producing interference patterns. The wave nature of light was not directly observable but was inferred from the pattern of light and dark bands.

Gregor Mendel's Pea Plant Experiments (1860s): - Genes

• Overview: Gregor Mendel conducted experiments on pea plants to study the inheritance of traits like flower color and seed shape. He cross-pollinated plants with different traits and observed the patterns of traits in the offspring.

• Inference: Mendel inferred the existence of "factors" (now known as genes) that are inherited in discrete units, even though he had no direct knowledge of DNA or chromosomes. His work laid the foundation for modern genetics.

Meselson-Stahl Experiment (1958): Semi-conservative nature of DNA replication

• Overview: Matthew Meselson and Franklin Stahl conducted an experiment to determine how DNA replicates. They grew bacteria in a medium containing heavy nitrogen (¹⁵N) and then switched to a medium with light nitrogen (¹⁴N). They used density gradient centrifugation to analyze the DNA after each generation.

• Inference: The experiment demonstrated that DNA replication is semi-conservative, meaning each new DNA molecule consists of one old strand and one new strand. This conclusion was drawn by observing the patterns of DNA density over generations.

Seismic Waves and the Earth's Interior - Earth's structure

• Overview: Geologists study the Earth's interior by analyzing seismic waves generated by earthquakes. These waves travel through the Earth and are detected by seismometers at various locations around the world.

• Inference: By observing how seismic waves are refracted, reflected, or absorbed as they travel through different layers of the Earth, scientists have inferred the existence of the Earth's core, mantle, and crust, as well as the liquid nature of the outer core. The internal structure of the Earth is not directly observable, but the behavior of seismic waves provides crucial insights.